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- 2080 Baisakh · 1+2 marks
- 2068 Baisakh · 1.5 marks
Unconformity and its types
Short answer
An unconformity is a buried erosion or non-deposition surface that represents a time gap in the rock record. Types include angular unconformity (younger beds over tilted older rocks), disconformity (parallel beds with irregular erosion surface), nonconformity (sediments on eroded igneous/metamorphic rocks), paraconformity (parallel, gap detected by fossils), and local unconformity (small break within a series due to local erosion).
What is unconformity? Describe the different types of unconformity with figures.
An unconformity is a surface of erosion or non-deposition that separates younger strata from older rocks and represents a gap (break) in the geological record.
Types of unconformity
- Angular unconformity - younger beds lie on tilted or folded older beds with an angular difference between them.
- Disconformity - younger and older beds are parallel, but separated by an irregular erosion surface.
- Nonconformity - sedimentary beds rest on eroded igneous or metamorphic (crystalline) rocks.
- Paraconformity - parallel beds with no visible erosion; the gap is known from fossils only.
- Local unconformity - a small break within the same series due to local erosion.
Angular Disconformity Nonconformity
___________ ___________ ___________
young beds young beds sedimentary
~~~~~~~~~~~ ~~~~~~~~~~~ ~~~~~~~~~~~
//tilted// old beds + + + + + +
//older/// (parallel) + igneous +
~~ = unconformity (erosion surface)
The unconformity surface is often marked by a basal conglomerate and a weathered zone.
✓ Answer checked by Claude Opus 5.5 (high effort)